EEPROM - the Holy Grail of Sideways Rom?

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MartinB
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Tue Aug 23, 2016 9:07 am

Ha!, you're mistaking me for someone who cares - it's a switch... :lol:

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby boba » Tue Aug 23, 2016 5:46 pm

:wink:

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MartinB
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Thu Aug 25, 2016 10:56 pm

As promised, here are the V4 utilities with the newly developed Master cartridge support as recently described. All the utils are at version 4.1A and this can be verified by launching a given command without specifying any parameters - e.g. *EELOAD <Return>

The zip contains DFS ssd and ADFS adf images where both include the three utilities and some test images. The programs are all ADFS compatible as long as PAGE does not exceed $1D00.

Any testing welcome including regression testing on Beebs and Elks please... [-o<

Member SteveF has previously drafted an info guide which is posted on Page 9 of the thread. I've still to review it properly and I suspect he's still waiting for answers to queries :oops: but perhaps he'll also contemplate updating it as some point with the new Master details if he's been monitoring the excitement... :)

===============================================================
A basic usage reminder of the utils for anyone unfamiliar....

*EELOAD <(filename) (@)> <id>

e.g. *EELOAD TESTAA 1

*EEP16 <(LOCK)(UNLOCK)(ERASE)(SUM)(OFF)> <id>

e.g. *EEP16 ERASE 2

*EEP32 <(LOCK)(UNLOCK)(ERASE)(SUM)(OFF)> <idL><idH>

e.g. *EEP32 UNLOCK 01


The EEP16 util applies to a 16k (single-eeprom, single-swrom) configuration (eeprom A14 and A12 shorted - see thread for details) and the EEP32 util applies to a 32k (single-eeprom, dual-swrom) configuration. EELOAD is used with both configurations.

Note that EELOAD and the EEPxx SUM and OFF commands can also be used with most standard sideways ram implementations.
===============================================================

V4 EEPROM Utilities 250816.zip
(3.63 KiB) Downloaded 48 times


EDIT 26-06-16 : Zip attachment updated to include an ADFS adf image in addition to a DFS ssd image.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby DutchAcorn » Fri Sep 30, 2016 10:20 pm

Here's something I've been wanting to try; an EEPROM is great but two is even better! :D

So here's a picture of a configuration with two installed:

The visible side:
eeprom top.jpg


And under the PCB:
eeprom under pcb.jpg


The flying leads are daisy chained which means the write protect switch is for all four banks simultaneously (that does limit the options; eg trying to use the EEPROM utilities from a DFS stored in an EEPROM fails).
Paul

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MartinB
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Sat Oct 01, 2016 12:01 am

=D>

As I always say, you can never have too many eeproms in 'yer Beebs... :D

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Fri Jun 16, 2017 10:09 pm

Sorry for bumping an old thread, but I thought it worth updating with confirmation that this flash chip works really well on the Computech IntegraB board with very little modification.

The only minor adjustment I needed to make was to disconnect nOE (pin22) of the flash from the rom socket on the IntegraB board, and connect it to nRDS on the main board (IC78 pin 9). I've set the jumpers on the IntegraB board to match the 32K RAM (non Battery Backup) configuration to ensure A14 and nWE signals are connected to the correct pins. I didn't have to cut any pins / wires / tracks on the IntegraB board or the flash ROM. I just used an intermediate Rom socket with pin 22 removed. I then made a small jumper cable with spring clips to connect between the nRDS line on the main board and nOE (pin 22) on each of the flash chips. I've installed 4 of these flash chips in the IntegraB board, one into each of the 32k ROM slots, giving me 8 x 16K EEPROM banks and 4 x 16K RAM banks on the IntegraB board, and the standard 4 x 16K ROM banks on the main board. All very cool 8) 8)

Edit: With some photos. Ignore the labels on the flash chips. That's just what I installed initially before having the facility to flash from the BBC. Oh, and you can't have too many filing systems! :lol: :lol:

Also, not sure why the first photo preview is upsides down. It's ok when you click on it and go full size. :?

20170616_233201.jpg

20170616_233420.jpg

20170616_233438.jpg

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MartinB
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Fri Jun 16, 2017 11:37 pm

Martin wrote:As I always say, you can never have too many eeproms in 'yer Beebs... :D

Well Ken, you certainly took that statement of mine to its literal limits.... :shock: :lol:

Looking good though =D>, are you using my programming utils or your own? Just curious to know if mine work with that config... :-k

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Fri Jun 16, 2017 11:41 pm

Yeah. That was with your EEP32 & EELOAD utilities, and they worked perfectly. My utilities are set to sector erase (not chip erase), and I don't think the 28C256 supports that mode?

Edit: Comparing datasheets, it looks like the 28c256 doesn't actually need an erase before write? Also, looks like you can write a 64 byte page to the 28c256 with a single write enable command sequence, whereas on the 128k flash each byte write needs to be enabled. I thought these things would all work the same way #-o. I'll need to have a proper review of your code!

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Sat Jun 17, 2017 12:15 am

Correct on all three counts - you don't need to erase before writing (I tend to just use erase for nulling sideways roms), yes, there is a 64-byte page write mode and no, there aren't any sectors.

I wrote some similar low-level programming utilities for Dave H's MGC and that 4Mb eeprom (an AM29F032B) also has all the opposite characteristics to those listed above.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby mjf2708 » Tue Jul 25, 2017 1:37 pm

Just installed an AT28C256 in a modified Sprow ROM / RAM Cartridge on my Master (thanks to daveejhitchins for EEPROM):

Image
Image

Working happily! :D

Mike

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Elminster
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby Elminster » Tue Jul 25, 2017 2:59 pm

Interesting I have a spare eeprom and I have a sprow cartiridge. I could probably work out what you did from the photo but if you could knock out some more notes that would be great. Another thing to add o my todo list.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby mjf2708 » Tue Jul 25, 2017 4:13 pm

Elminster wrote:knock out some more notes...

OK, here goes:

- cut track connecting centre and top holes on L1 - top of board(assuming default configuration of Sprow board)
Image
- cut track connecting centre and bottom holes on L2 - bottom of board
Image
- connect centre of switch to centre hole of L1 (note: all connections are to PTH's on board)
- connect top of switch (write protect on) to 5V rail
- connect bottom of switch (write protect off) to top hole of L1
- connect centre hole of L2 to A22 (0V)
- lift pin 1 of EEPROM and connect to bottom hole of L2

HTH,

Mike

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Elminster
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby Elminster » Tue Jul 25, 2017 4:47 pm

Great thanks. Will give it a go at some point. Worst case Sprow get an order for another ROM Card :)

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Mon Nov 13, 2017 1:00 pm

I've been doing a bit of reverse engineering of my IntegraB board over the weekend, and discovered that the board actually generates its own nRDS signal (and nWDS), and this is wired to pin 22 (nOE) of each ROM socket, and all three SRAM chips, so in theory I shouldn't need the jumper wires I installed previously (see my earlier post above).

When re-installing the board in my beeb, I decided to leave out the jumper wires and rely on the IntegraB generated nRDS signal.

Unfortunately, the 28C256 doesn't seem to be working correctly any more. I think the EEP32 and EELOAD utilities are doing their job. EELOAD verifies fine after a write, but when I then try running something from the EEPROM I start getting odd behaviour. A power cycle doesn't fix it. I'm not sure if it's because the image becomes corrupt in the EEPROM, or if data is not getting read correctly from the EEPROM when I'm trying to run code from it. I'm confident that the raw images on disk are fine, because I can load them into a spare RAM bank and they work ok.

Further work required to find out what's going wrong. Not sure if it's actually related to the nRDS signal, but I'll start by going back to the nRDS that's generated on the main beeb board...

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Mon Nov 13, 2017 10:04 pm

So, I'm struggling to see what's going wrong here. I've tried both the Beeb generated nRDS and the IntegraB generated nRDS and both give the same results.

I can unlock the 28C256 EEPROM and program both the upper and lower bank without any problem. For my test I'm using the ViewSheet & ViewStore ROMs. Both work fine if I load them into the SWRAM bank (if I then Write Protect it). I've tried various EEPROMs, and swapped the order in which the two ROMS are programmed into the EEPROM. I've also tried plugging the EEPROM into various banks (8/9, A/B & C/D).

Both ROMS load and verify without any issue. As long as I write protect the EEPROM (by applying 5V to the EEPROM RW pin), the upper bank seems to work fine, but when I then try to run the software in the lower bank it causes the BBC to crash or error out (it's not consistent). Other points of note:

* nRDS from the IntegraB board is wired to pin 22 of the EEPROM. I've also tried nRDS from the main Beeb board.
* nWDS (again, generated from the IntegraB board) is wired to pin 27 of the EEPROM. I can change this to 5V Write Protect via jumpers on the IntegraB board.
* D0 from a &FE30 ROMSEL data latch on the IntegraB board is wired to pin 1 (A14) of the EEPROM to switch between the upper and lower banks.
* Pin 20 (nCE) from the EEPROM is wired to 4 / 16 line decoder (74159). Actually, 2 lines from the decoder are tied together, so that nCE is driven by either one of two outputs from the decoder. This allows 2 x 16k banks access to the one 32k EEPROM.
* 32k ROMS seem to work ok - when I move the jumpers on the board to make sure A14 is addressed via pin 27.

What am I missing? It's driving me mad!

I might actually try some 29C256 flash memory instead to see if it works any better.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby hoglet » Mon Nov 13, 2017 10:54 pm

Are your 28C256s from a reputable source? There are lots of fakes on ebay.

Dave

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Mon Nov 13, 2017 11:18 pm

Most likely not a reputable source... unless china suppliers are now considered reputable :roll:

Perhaps that was the problem. I just didn't understand why the EEPROM write / verify routine was working, but subsequent reads weren't working. I suspect, however, I may have had a more fundamental issue, because things started failing when loaded to my SWRAM as well.

I've subsequently replaced the 'suspect' EEPROM and re-seated all other ROMS / ICs, and everything seems to be working a bit better again. I'm hoping that's solved the problem, but I'm not convinced yet.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Mon Nov 13, 2017 11:30 pm

As a sanity check (and although this one’s maybe a pain :roll:), could you first revert to a ‘normal’ Beeb again without the IntegraB and configure one of your 28C256’s in the originally prescribed manner? That would at least vindicate the eeprom chips (or otherwise) without you having to try a different type. Trouble is, it’s hard for me (or perhaps anyone) to comment significantly on the IntegraB configuration because I don’t have one and my normal instinct would be to scope the relevant signals to try and better understand the (bad) behaviour.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Mon Nov 13, 2017 11:41 pm

Scoping was going to be my next line of attack, but it all seems to be working now, with 4 x 28C256 EEPROMs covering banks 8..15. I've managed to ditch the flying leads I was using previously and I'm using the signal generated on the IntegraB board instead. Once I've programmed the EEPROM, I'm now switching the WP on, so that may be making the difference.

I'm reluctant to remove the IntegraB now that it all seems to be working, but if it fails again, I can easily remove the board, and put the EEPROM into one of the original sockets.

Thanks for the suggestions, guys.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby Mekon » Wed Nov 15, 2017 10:37 pm

I seem to be having some trouble unlocking my EEPROMS too. I'm using a master and I've added a write-protect switch to a care electronics cartridge as detailed somewhere further back in this thread. This being the simplest possible mod, it seemed like a good place to start.

Using version 4.1A of the utils, I can use *EEP16 to unlock the EEPROM, but as soon as I try to do anything else, it tells me it's locked again.

Any ideas?

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Wed Nov 15, 2017 11:19 pm

Are you using the correct EEP:

Code: Select all

If *EELOAD gives a message "EEPROM Locked", this indicates that the EEPROM has
been "soft-locked"; this is an extra (and TODO: optional?) level of protection in
addition that provided by the write-protect switch. You need to use the *EEP16
or *EEP32 command to unlock it:

- Where you chose the 16KB option during construction, the *EEP16 command must
  be used. To unlock bank &F, for example, do: *EEP16 UNLOCK F

- Where you chose the 32KB option during construction, the *EEP32 command must
  be used. This needs to be told *both* banks at which the EEPROM appears in
  order to work. Soft-locking applies to the entire 32KB EEPROM, not
  independently to each 16K bank. Suppose for example you have chosen the 32KB
  option and installed the EEPROM in socket IC101 of a BBC B with the pin 1
  flying lead connected to IC76 pin 12. As shown in the table in the
  construction section, the EEPROM will appear in banks &B and &F, so to unlock
  the EEPROM you need to use the command: *EEP32 UNLOCK BF

You should receive an "Ok" message if the unlock is successful; you can then
retry the EELOAD command.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Wed Nov 15, 2017 11:33 pm

Right. I *think* I'm getting to the bottom of my issues. I suspect the *EEP32 LOCK command is corrupting the lower bank. If I program the ROM then do a soft lock, I get issues with the ROM in the lower bank. If I program the ROM and leave it unlocked, then the ROM in the lower bank seems to work fine. I've got external write protect that I can use instead of the soft lock. I'll run a compare before and after soft lock to see if / where the corruption is occurring. I'm running V4.1A of the EEP32 utility.

Edit: Well, after doing a compare, I can verify that the EEPROM hasn't been corrupted by soft lock. :-? However, soft lock is definitely preventing the lower ROM bank from working correctly. Unlocking gets it working again.
I'm also confident that all my EEPROMs are working correctly. I've been able to test and verify them all on an external programmer.
The most reliable way to get it working is to leave the soft lock off, and use the WP switch to prevent any writes from occurring.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Thu Nov 16, 2017 7:28 am

@Mekon - You mentioned a write-protect switch but how have you otherwise configured the eeprom in the cartridge? I published details of how to modify a Master or Elk cartridge to take a single AT28C256 device configured as a 32k 2-rom unit and in that instance, you need to use the EEP32 configuration tool together with EELOAD and not EEP16 as you infer. EEP16 would still go through the motions but wouldn't actually lock the eeprom.

Edit : Just realised that you've done the mod as per further up this thread so ignore the Elk stuff but the comments regarding the use of EEP32 over EEP16 and the following note does still very much apply to you....

Assuming you are then using the correct EEPx util tool, it's also always better to use the EEPx 'OFF' switch before any configuration changes or loading, finally finishing with a <Ctrl><Break> to reset the machine. This is particularly true of the Master and Elk where 100Hz rom polling is employed.

@Ken - Are you also using the EEP32 OFF switch prior to locking/unlocking and programming? If so and your're still having problems, first revert to a stock Beeb to simplify the configuration and if the eeproms are still playing up, it would lend credence to hoglet Dave's suggestion regarding hooky and/or suspect devices.
Last edited by MartinB on Thu Nov 16, 2017 11:45 am, edited 2 times in total.

KenLowe
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Thu Nov 16, 2017 10:53 am

MartinB wrote:@Ken - Are you also using the EEP32 OFF switch prior to locking/unlocking and programming?

Short answer is no. I wasn't aware of that switch. I'll try that this evening and report back.

MartinB wrote:it would lend credence to hoglet Dave's suggestion regarding hooky and/or suspect devices

I'm fairly sure there's nothing wrong with the EEPROMs. They lock / unlock and can be programmed / read using an external programmer without any issue. I've got another unexpanded BBC that I can use to test the EEPROMs which should eliminate the IntegraB as a source of problem. Again, I'll try that this evening.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Thu Nov 16, 2017 12:28 pm

Ken wrote:Short answer is no. I wasn't aware of that switch. I'll try that this evening and report back.

Its generally not as critical on a Beeb, it tends to depend on what's already in the eeprom prior to any change. If the eeprom is already empty or full of garbage then the OFF command likely won't make any difference.

There's also an EEPxx SUM switch which is useful for chasing suspected corruptions because it gives you the Checksum-32 for a given 16k (or x2 for a 32k) and you can invoke it any time, not just when programming.

Note that for both EEPxx OFF and SUM, the syntax requires either a single hex rom id for EEP16 or a dual id for EEP32. So, for example if your 32k eeprom is configured to appear as rom id's B and F, to turn the device off you'd use *EEP32 OFF BF or *EEP32 SUM BF for the checksum. EEP16 just requires a single hex rom id.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Thu Nov 16, 2017 6:41 pm

Still with the EEPROMs in my IntegraB board, but interestingly:

Code: Select all

<CTRL><BREAK>
>*EEP32 UNLOCK AB
EEPROM Locked
Unlocking...   Ok
>*EELOAD BASICED A
Programming : $BFFF
Verifying :   $BFFF
Checksum-32 = $001A9F48
Finished.
>*EELOAD HIBASIC B
Programming : $BFFF
Verifying :   $BFFF
Checksum-32 = $001C2E4F
Finished.
>*EEP32 LOCK AB
Ok

<CTRL><BREAK>
>*EEP32 SUM AB
Checksum-32 = $001A9FAF : $001C2E4F

>*BE
***Machine hangs***

<CTRL><BREAK>
>*EEP32 UNLOCK AB
EEPROM Locked
Unlocking...   Ok
<CTRL><BREAK>
>*EEP32 SUM AB
Checksum-32 = $001A9F48 : $001C2E4F

>*BE
***Basic Editor loads correctly***

<CTRL><BREAK>
>*EEP32 LOCK AB
Ok
<CTRL><BREAK>
>*EEP32 SUM AB
Checksum-32 = $001A9FAF : $001C2E4F

>*BE
***Machine hangs again***


This is 100% repeatable with multiple EEPROMs. I'll try and find out exactly which bytes are being corrupted. After that I'll try this again in an unexpanded BBC.

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dv8
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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby dv8 » Thu Nov 16, 2017 8:04 pm

Ken,

This hanging issue can be caused by something trying to write to the ROM address space. Even if the EEPROM is soft locked it still has to respond to commands. Any write to the EEPROM will put it into 'listen' mode and any subsequent read will return status information rather than ROM data for a short period of time.

The main culprits are ROMs that try to write to themselves (e.g. as a form of copy protection check) or utility ROMs that check all banks for the presence of sideways RAM, like some ROM managers or the SRAM utils that are part of DFS 2.26.

The only way to avoid the problem is to use a hardware write protect (i.e. prevent /WE from being pulled low), or to avoid using the offending ROMs.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby MartinB » Thu Nov 16, 2017 8:24 pm

Yes, that is indeed correct and this effect and the consequent need for a hardware write protect switch is actually all fully documented in the thread. So dv8 is correct and you (Ken) will almost certainly find that everything behaves as it should if you always apply hardware write-protect after programming.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Thu Nov 16, 2017 9:21 pm

Hi,

I was aware of the glitches that can occur when trying to write to the ROM when soft locked, which is why I have WP switches on all the EEPROM banks. However, the issue I have is a bit different. If I read the checksum from the EEPROM when unlocked, I get a different result compared to when I read the checksum when locked. Locking the EEPROM appears to cause 'corruption' of at least one byte of data from the lower bank. Unlocking it again fixes the corruption.

Once locked, the ROM in the lower EEPROM bank remains corrupt regardless of the position of the WP switch
When unlocked, the ROM in the lower EEPROM bank will normally work regardless of the position of the WP switch, but some ROMS do require the WP switch to be active to avoid glitches during attempted writes to the EEPROM.

I've installed one of the EEPROMs into another of my Beebs and I'm seeing similar results. The EEPROM is plugged into ROM socket 100. EEPROM pin 1 (A14) is wired to IC76 pin 12, pin 22 (nOE) is wired to IC73 pin 25 (nRDS) and pin 27 (nWE) is wired to IC73 pin 24 (nWDS). The EEPROM is visible in banks A&E. Still working on it, because I'm seeing some other unexplained behaviour.

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Re: EEPROM - the Holy Grail of Sideways Rom?

Postby KenLowe » Thu Nov 16, 2017 9:40 pm

To confuse matters, I think there's an issue with EEP32 SUM command. It looks like the wrong upper bank is being used to calculate the checksum (under some circumstances - in this case with the EEPROM in banks A&E):

20171116_213358.jpg


Regardless of the issue with calculating the checksum of the upper block, I am definitely seeing the same 'corruption' issue on the lower bank when I carry out a soft lock on this unexpanded beeb:

20171116_214330.jpg


if I remove the soft lock, I get the original (and correct) checksum.

Edit: Ok. A bit more info. When soft lock is being applied, byte 0 of the EEPROM is being 'corrupted'. It is being XORd by &FF. Could this be EEP32 doing a check for writable EEPROM? This might also explain why it takes 2 unlock attempts to correct the problem - since the rom is locked, the XOR check can't actually write to the first byte on the first occasion. This can only happen on the second occasion after the soft lock is removed???
Last edited by KenLowe on Thu Nov 16, 2017 10:54 pm, edited 2 times in total.


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